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From: diamant@hpfclp.SDE.HP.COM (John Diamant)
Newsgroups: comp.windows.x
Subject: Re: How can I implement a query window at position ?
Message-ID: <9740100@hpfclp.SDE.HP.COM>
Date: 21 Aug 89 05:56:01 GMT
References: <8908121716.AA12203@expo.lcs.mit.edu>
Organization: HP SESD, Fort Collins, CO
Lines: 40

> I would like to find out what is the window at a certain screen position.
> Is there any way to do it without using the hack about warping the mouse
> to that position and do a XQueryPointer and then warp back the mouse.
> My current hack cannot work when you have EnterNotify and LeaveNotify set.

You can use XTranslateCoordinates.  For example, here's a piece of code
I use to find the smallest window in which the pointer was when the
function was called (it expected a call to XQueryPointer to be done
prior to the call, but you could pass in the root window and the x y
coordinates instead):

void find_smallest_window(dpy, parent, child, win_x, win_y)
   Display *dpy;
   Window *parent, *child;
   int win_x, win_y;
{
   Window win;
   
   if (!child)
      child = parent;
   
   /* Note: The function XTranslateCoordinates must be used instead of	     */
   /*	 XQueryPointer to avoid dependence on the pointer remaining	     */
   /*	 stationary.  This eliminates the race condition of the pointer	     */
   /*	 moving, but not the one of the window hierarchy changing	     */
   
   while (XTranslateCoordinates(dpy, *parent, *child,
				win_x, win_y,
				&win_x, &win_y, &win)
	  && win != NULL) {
      *parent = *child;
      *child = win;
   }
}


John Diamant
Software Engineering Systems Division
Hewlett-Packard Co.		Internet: diamant@hpfclp.sde.hp.com
Fort Collins, CO		    UUCP: {hplabs,hpfcla}!hpfclp!diamant